(1). Technical Field
This invention is concerned with improvements to the manufacturing methods for magnetic disk drives, and more particularly to an improved method for the assembly of a voice coil motor (VCM) used in magnetic disk drives, the components of which can be fabricated at a lower cost with greater accuracy.
(2) Description of the Prior Art
Voice coil motors, an integral driver device used for positioning magnetic heads in magnetic disk apparatus, are customarily used in numerous operations because of its structural simplicity and excellent performances as a driver for low inertia, high speed motions. In a magnetic disk apparatus, which is required to bring about fast and precision movements of a magnetic head from a particular disk position to another, using a voice coil motor needs less access time than other types of motors, therefore, are the most popular and widely used drivers for positioning magnetic heads in computer disk drives.
The following five documents relate to methods dealing with improvements to voice coil motors used on disk drives assemblies.
U.S. Pat. No. 5,051,669 issued Sep. 24, 1991 to Hsiao, et al, describes a voice coil motor provided with a set of improved shorted turn.
U.S. Pat. No 5,193,037 issued Mar. 9, 1993 to Pace, discloses a compact disk drive which is significantly reduced in overall length and depth.
U.S. Pat. No 5,177,383 issued Jan. 5, 1993 to Jun-seok Sim, discloses a voice coil motor which conveys a head of optical or magneto-optical disk or magnetic disk drive as a kind of linear motor.
U.S. Pat. No 5,424,591 issued Jun. 13, 1995 to Kuriyama, shows a compact disk drive yoke with a plurality of thin plates coated with a corrosion resistant material.
U.S. Pat. No 5,585,981 issued Dec. 17, 1996 to Lee, discloses an improved voice coil motor fastening device for a hard disk drive.
Typically, a voice coil motor is assembled from several parts and is then incorporated into a magnetic disk drive. A disk drive used as an auxiliary computer memory is a device manufactured with a high degree of precision. Several fastening methods for holding the parts together are used. Generally, fasteners such as screws were used to enable the completed product to be serviced when defective. As anticipated, however, the inclination within the industry was to merely reject defective assemblies rather than rework them which led to a different fastening method using adhesives. This led to a new set of processing problems involving adhesives which are still being evaluated. Outgassing and long term effects on materials within the hard disk drive, connective strength of the adhesive, curing time and adhesive fatigue are a few of such concerns.
FIG. 1, is a side view illustrating a voice coil motor 10 of the prior art, is produced by putting together essential parts, as shown in an exploded view in FIG. 2, typically including, an arcuate shaped top plate 5 having an upper 2 and lower surface, a matching bottom plate 6, two posts 3 and 4 used for spacing the plates apart, and a permanent magnet 8 disposed on the upper surface of the lower plate 6. The parts are usually joined together by indirect contact, for example, using an adhesive 9 interposed between the respective parts, or by direct contact using screw fasteners (not shown). FIGS. 3A and 3B show a top view of the top and bottom plates 5 and 6, respectfully, along with the side posts 3, 4. The permanent magnet 8 is shown disposed on the top surface of the lower plate 6 As alluded to earlier, the application of adhesives have several long term concerns, such as, outgassing, connective strength, and adhesive fatigue, there are also other assembly problems using adhesives. Among them are; contamination caused by poor application of the adhesive, controlling the spread of the layer of adhesive to within the outside boundaries of the parts, holding the parts within the magnetic field, and managing the storage and retrieval of parts for assembly.
It is therefore a primary object of the invention to provide an improvement over the prior art methods for assembly of the voice coil motor by minimizing the number of parts which will reduce cost while improving the overall design.
It is another object of the invention is to provide a more compact, space reducing assembly when the voice coil motor is fastened to a hard disk drive.
It is another object of the invention to reduce foreign material, such as adhesives, from the disk drive so that long term effects from outgassing from the adhesives, during curing is reduced and all other associated factors such as corrosion, contamination and other potentially harmful factors.
The foregoing objects of the invention are accomplished and the disadvantages of the prior art overcome by the provision of a disk drive including a voice coil motor assembly which is assembled without the use of adhesives.
To accomplish the objects of the present invention, there is provided a design of a voice coil motor that is assembled from fewer parts. This is achieved with a metal injection molded part that combines the function of several of the conventional parts into one. Moreover, features are designed within the molded part to releasably secure the magnets without the use of adhesives or fasteners.